Lan Zhaohui, Xu Jinling, Wang Youji, Lu Weiqun
National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China.
National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China.
Gen Comp Endocrinol. 2018 May 15;261:9-22. doi: 10.1016/j.ygcen.2018.01.017. Epub 2018 Jan 31.
A neuromodulatory role for glutamate has been reported for magnocellular neuroendocrine cells in mammalian hypothalamus. We examined the potential role of glutamate as a local intercellular messenger in the neuroendocrine Dahlgren cell population of the caudal neurosecretory system (CNSS) in the euryhaline flounder Paralichthys olivaceus. In pharmacological experiments in vitro, glutamate (Glu) caused an increase in electrical activity of Dahlgren cells, recruitment of previously silent cells, together with a greater proportion of cells showing phasic (irregular) activity. The glutamate substrate, glutamine (Gln), led to increased firing frequency, cell recruitment and enhanced bursting activity. The glutamate effect was not blocked by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801, or the GluR1/GluR3 (AMPA) receptor antagonist IEm1795-2HBr, but was blocked by the broad-spectrum α-amino-3-hydroxy- 5- methyl-4-isoxazo-lepropionic acid (AMPA) receptor antagonist ZK200775. Our transcriptome sequencing study revealed three AMPA receptor (GluR1, GluR2 and GluR3) in the olive flounder CNSS. Quantitative RT-PCR revealed that GluR2 receptor mRNA expression was significant increased following dose-dependent superfusion with glutamate in the CNSS. GluR1 and GluR3 receptor mRNA expression were decreased following superfusion with glutamate. L-type Ca channel mRNA expression had a significant dose-dependent decrease following superfusion with glutamate, compared to the control. In the salinity challenge experiment, acute transfer from SW to FW, GluR2 receptor mRNA expression was significantly higher than the control at 2 h. These findings suggest that GluR2 is one of the mechanisms which can medicate glutamate action within the CNSS, enhancing electrical activity and hence secretory output.
据报道，谷氨酸在哺乳动物下丘脑的大细胞神经内分泌细胞中具有神经调节作用。我们研究了谷氨酸作为一种局部细胞间信使，在广盐性比目鱼（ Paralichthys olivaceus）尾神经分泌系统（CNSS）的神经内分泌达尔格伦细胞群中的潜在作用。在体外药理学实验中，谷氨酸（Glu）使达尔格伦细胞的电活动增加，使先前沉默的细胞被激活，同时有更大比例的细胞呈现相位性（不规则）活动。谷氨酸底物谷氨酰胺（Gln）导致放电频率增加、细胞被激活以及爆发活动增强。谷氨酸的作用未被N-甲基-D-天冬氨酸（NMDA）受体拮抗剂MK-801或GluR1/GluR3（AMPA）受体拮抗剂IEm1795-2HBr阻断，但被广谱α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体拮抗剂ZK200775阻断。我们的转录组测序研究揭示了比目鱼CNSS中有三种AMPA受体（GluR1、GluR2和GluR3）。定量逆转录聚合酶链反应（RT-PCR）显示，在CNSS中用谷氨酸进行剂量依赖性灌流后，GluR2受体mRNA表达显著增加。用谷氨酸灌流后，GluR1和GluR3受体mRNA表达降低。与对照组相比，用谷氨酸灌流后，L型钙通道mRNA表达呈显著的剂量依赖性降低。在盐度挑战实验中，从海水急性转移到淡水后，GluR2受体mRNA表达在2小时时显著高于对照组。这些发现表明，GluR2是介导谷氨酸在CNSS内发挥作用、增强电活动从而增加分泌输出的机制之一。
